The fabrication of semiconductor devices, such as logic and memory devices, typically includes processing a semiconductor device using a large number of semiconductor fabrication and metrology processes to form various features and multiple layers of the semiconductor devices. Select fabrication processes utilize photomasks/reticles to print features on a semiconductor device such as a wafer. As semiconductor devices become smaller and smaller laterally and extended vertically, it becomes critical to develop enhanced inspection and review devices and procedures to increase sensitivity and throughput of photomask, reticle, and wafer inspection processes.
One inspection technology includes electron beam-based inspection such as scanning electron microscopy (SEM). In some instances, scanning electron microscopy is performed via secondary electron beam collection (e.g., a secondary electron (SE) imaging system). In other instances, scanning electron microscopy is performed by splitting a single electron beam into numerous beams and utilizing a single electron-optical column to individually tune and scan the numerous beams (e.g., a multi-beam SEM system). In other instances, scanning electron microscopy is performed via an SEM system which includes an increased number of electron-optical columns (e.g., a multi-column SEM system).
SEM systems include electron beam sources that generate electron beams utilized to characterize a photomask/reticle or wafer. Traditionally, the electron beam sources each include an electron emitter with an emitter tip. When an emitter tip burns out, all electron beam sources must be removed from the SEM system. Where the electron beam sources are coupled together in a single assembly, the ultra-high vacuum (UHV) environment in which the SEM system operates must be broken so the burnt-out tip may be replaced. Repairing the burnt-out electron beam source, reinstalling the electron beam source, and restoring the UHV environment may result in a downtime measured in weeks and repair costs measured in the tens of thousands of dollars.
The electron beams generated by the electron beam sources are extremely sensitive to misalignment, to the order of microns, such that misalignment may occur from improper installation of the electron beam sources, system jitter, emitter tip expansion when heated, or the like. To correct for the misalignment, each electron emitter of an electron beam source is coupled to a stack of positioners. The stack of positioners is manually adjusted from the atmospheric side of the UHV to prevent the breaking of the UHV. The manual adjustment is monitored via visual or emission feedback and can be lengthy in time and/or tedious in nature. In addition, the manual alignment is completed on a per-emitter basis, and does not allow for the simultaneous alignment of multiple emitters. Further, the manual alignment when the SEM system is not operational may be negated at least in part by the expansion of a heated emitter tip when the SEM system is operational. This, combined with the sensitivity of the stack of positioners to the heat generated by the emitter tip during operation, causes considerable difficulty with aligning the electron beams.
Therefore, it would be advantageous to provide a system and method that cures the shortcomings described above.